1. Field of the Invention
The invention generally relates to a data protection method, and more particularly, to a data protection method for damaged memory cells.
2. Description of Related Art
Along with the development of electronic technology, storage media has become a key factor in information exchange, wherein memory has become the most indispensable storage medium for computers thanks to its high operation speed. However, since the requirement to transmission speed has increased with the increasing data transmission capacity, the demand to large-capacity and high-speed memories has increased too.
However, at the same time of increasing the capacity of a memory, the density of memory cells in the memory is also increased. Accordingly, the size of each memory cell has to be reduced when the density of semiconductor memory devices in an integrated circuit (IC) is increased. Thus, the process for fabricating memory cells of reduced size without sacrificing the original capacitance thereof becomes very complicated, and more errors are likely to be produced in such memory cells when the system access speed is high.
Errors produced in a memory may be correctable errors (CEs) or uncorrectable errors (UEs). A CE is usually a single bit error (SBE) or a multi-bit error (MBE) in which the number and position of the error bits are within a correctable range of an electronic device. A CE can be flexibly corrected through an error detection and correction (EDC) technique. Conventionally, a spare memory module is configured in a memory such that data can be backed up when a CE is detected in the memory. However, the spare memory takes up a lot of memory space therefore causes the memory space to be wasted. Besides, because the operation for backing up data into the spare memory takes a long time, the performance of the entire system is reduced.
On the other hand, conventionally, half of a memory is configured as a mirror memory, and the mirror memory is used for data correction when an UE is detected in the memory. However, because the mirror memory takes up half of the space of the system memory, waste of memory space is caused and the performance of the entire system is reduced. Additionally, in foregoing data mirroring backup technique, every time when data is written or read, both the original memory and the mirror memory have to be accessed in order to keep data in both memories consistent. Thereby, more system resources are consumed.